The present invention relates generally to a transcritical vapor compression system including an auxiliary electric heater that further heats the water that exchanges heat with the refrigerant in the gas cooler.
Chlorine containing refrigerants have been phased out in most of the world due to their ozone destroying potential. Hydrofluoro carbons (HFCs) have been used as replacement refrigerants, but these refrigerants still have high global warming potential.
“Natural” refrigerants, such as carbon dioxide and propane, have been proposed as replacement fluids. Carbon dioxide can be used as a refrigerant in automotive air conditioning systems and other heating and cooling applications. Carbon dioxide has a low critical point, which causes most air conditioning systems utilizing carbon dioxide as a refrigerant to run transcritically, or partially above the critical point, under most conditions.
A vapor compression system usually operates under a wide range of operating conditions. When the outdoor air temperature varies, the temperature of the refrigerant exiting the evaporator varies. Therefore, the heating capacity of the vapor compression system in the summer is generally four to five times greater than the heating capacity of the vapor compression system in the winter, and the refrigerant mass flow rate of the vapor compression system in the summer is generally eight to ten times greater than the refrigerant mass flow rate of the vapor compression system in the winter. Although the heating capacity of the system changes as the operating conditions change, the required heating load of the system does not change as the operating conditions change.
A vapor compression system must be able to provide enough heating capacity to meet the load requirements during the winter when the outdoor air temperature is the lowest. In the prior art, the vapor compression system is oversized to provide enough heating capacity in the winter. However, oversizing the vapor compression system causes the heating capacity to be higher than necessary for most of the ambient conditions, significantly increasing cost.
Hence, there is a need in the art for a vapor compression system that has a high heating capacity and is cost effective. This invention includes an auxiliary electric heater that further heats the water that exchanges heat with the refrigerant in the gas cooler.